Soybean loopers are having a field day this year in N.C. soybean fields, notes N.C. State University entomologist Jack Bacheler. Bacheler addressed the issue in the most recent issue of N.C. Pest News, a newsletter put out by the NCSU Departments of Entomology and Plant Pathology. Bacheler terms the insect levels of the pest "plague-like."
Data in the newsletter from Extension entomologist Ames Herbert, Virginia Tech University, indicates, "In one trial, two days after treatment, the best insecticides were spinosad (Success, 3 ounces per acre) and spinetoram (a more active form of spinosad, labeled as Radiant SC, 4 ounces per acre). In an adjacent trial, 2 days after treatment, Steward was the best insecticide, with the 6 and 8 ounces per acre rates giving equivalent results. Larvin at 16 ounces per acre was also excellent, as was Belt at 3 ounces per acre. Decreasing the rates of both Larvin and Belt provided slightly less numerical control, but not significantly less."
Fellow NCSU Extension entomologist Dominic Reisig noted bean leaf beetles are also a problem in soybeans, with some growers reporting failures of pyrethroid insecticides.
"This is most likely a function of bean leaf beetle movement and how soon soybeans are checked after treatment," Reisig says. Bean leaf beetles can move from untreated fields into treated fields where the residual insecticide is breaking down.
Clothianidin and pyrethroids are probably the best options for management, he adds. In a trial those products had effectiveness up to a week after treatment.
You can read the complete issue of North Carolina Pest News by downloading a .pdf form from ipm.ncsu.edu/current_ipm/pest_news.html